Ash and smoke are spewed from Popocatepetl Volcano as seen from the city of Puebla, in the Mexican central state of Puebla, on April 18. Residents of nearby communities reported roaring noises from the Popocatepetl volcano near Mexico City on Tuesday after signs of increased activity prompted authorities to raise alert levels.

Imelda Medina / Reuters

A boy helps another adjust his surgical mask, which were handed out by the Red Cross, in San Nicolas de los Ranchos April 17. A powerful plume of steam and ash rose from the Popocatepetl volcano in central Mexico on Tuesday, prompting local schools to cancel classes and emergency teams to prepare for evacuations. Mexico's National Center for Disaster Prevention raised the alert level for the 5,450-meter (17,900-foot) Popocatepetl, which lies some 50 miles to the southeast of Mexico City, late on Monday.

Francisco Guasco / EPA

View of a shelter in Santiago Xalitzintla, in the Mexican state of Puebla, prepared due to an alert status phase three issued by the National Center for Prevention of Disasters on April 17. According to the National Center for Prevention of Disasters, the volcano Popocatepetl has spewed some ash emissions and sproadic explosions of low and moderate level.

Imelda Medina / Reuters

The Popocatepetl volcano spews a cloud of ash and steam high into the air, as seen from San Nicolas de los Ranchos, on the outskirts of Puebla April 18. A powerful plume of steam and ash rose from the Popocatepetl volcano in central Mexico on Tuesday, prompting local schools to cancel classes and emergency teams to prepare for evacuations. Mexico's National Center for Disaster Prevention raised the alert level for the 5,450-meter (17,900-foot) Popocatepetl, which lies some 50 miles to the southeast of Mexico City, late on Monday.

From Reuters: SAN PEDRO BENITO JUAREZ, Mexico — A powerful plume of steam and ash rose from the Popocatepetl volcano in central Mexico on Tuesday, prompting local schools to cancel classes and emergency teams to prepare for evacuations.

The volcano's lava dome started to expand on Friday, suggesting fresh magma may be pushing upwards. It spewed red-hot fragments and lightly dusted cars and streets in some small towns in the state of Puebla, television images showed.

Popocatepetl, which lies some 50 miles to the southeast of MexicoCity, pumped out a cloud of hot air and particles in an emission lasting about 20 minutes on Tuesday. "It sounded like a loud cauldron releasing steam," said Reuters cameraman Roberto Ramirez.